title: Mechanical hyperalgesia is attenuated by local administration of octreotide in pristane-induced arthritis in Dark-Agouti rats.
abstract: OBJECTIVE
  The Dark-Agouti (DA) rat is very susceptible to pristane-induced arthritis (PIA) and represents a suitable model for rheumatoid arthritis. In the present study, we examined the pain sensitivity and the effect of local administration of octreotide (OCT) on mechanical hyperalgesia in PIA DA rats.
  
  
  METHODS
  Arthritis was induced by intradermal injection of pristane (300 microl). The mechanical withdrawal threshold (MWT) and heat withdrawal latency (HWL) were used to evaluate the pain sensitivity. In addition, we recorded the discharge firings in the tibial nerve sensory C-fibers innervating the inflamed toe joints of arthritic DA rats.
  
  
  RESULTS
  Two weeks after injection of pristane, all DA rats developed severe arthritis. This symptom was associated with a decreased MWT (78.50+/-5.68 mN before pristane injection, 19.50+/-6.27 mN on day 14 after pristane injection), indicating a mechanical hyperalgesia in PIA. In contrast, HWL was comparable before and after pristane injection (10.25+/-0.70 s before injection; 9.45+/-1.23 s on day 14 after injection). Local injection of OCT markedly increased MWT and relieved the hyperalgesia in PIA. In addition, OCT significantly decreased the discharge rate of afferent C units evoked by both non-noxious and noxious joint movements.
  
  
  CONCLUSIONS
  Taken together, the results demonstrate that mechanical hyperalgesia, but not thermal hyperalgesia is associated with PIA and that the mechanical hyperalgesia and the discharge of afferent C units are attenuated by local administration of OCT. These observations provide evidence for a novel therapeutic strategy for pain control in rheumatoid arthritis.
authors.affiliation: Department of Physiology and Pathophysiology, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi 710061, PR China.
authors.forename: Fanrong
authors.initials: F
authors.lastname: Yao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Guo
authors.forename: Shemin
authors.initials: S
authors.lastname: Lu
authors.forename: Chengwen
authors.initials: C
authors.lastname: Sun
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.forename: Huisheng
authors.initials: H
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000150:complications*; D001522:Behavior, Animal / Q000187:drug effects; D004594:Electrophysiology; D006930:Hyperalgesia / Q000188:drug therapy* / Q000209:etiology*; D007166:Immunosuppressive Agents; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D015282:Octreotide / Q000627:therapeutic use*; D010147:Pain Measurement / Q000187:drug effects; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D013729:Terpenes
chemical_list: D007166:Immunosuppressive Agents; D013729:Terpenes; C009042:pristane; D015282:Octreotide